Some physical parameters of CuInGaS2 thin films deposited by spray pyrolysis for solar cells

Abstract

Copper–indium–gallium–disulphide (CuInGaS2) is a promising absorber material for thin film photovoltaic. In this paper, CuInGaS2 (CIGS) thin films have been prepared by chemical spray pyrolysis method onto glass substrates at ambient atmosphere. Structural, morphological, optical and electrical properties of CuInGaS2 films were analysed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV–Vis spectrophotometer and Hall Effect measurement, respectively. The films exhibited single phase chalcopyrite structure. The strain and dislocation density decreased with increase of spray time. The grain size of the films increased from 4.45 to 9.01 nm with increase of spray time. The Raman spectrum indicated the presence of the principal chalcopyrite peak at 295 cm\(^{-1}\). The optical properties of the synthesized films have been carried out through the measurement of the absorbance spectrum. The optical band gap was estimated by the absorption spectrum fitting (ASF) method. For each sample, the width of the band tail (\(E_\mathrm{Tail}\)) of CuInGaS2 thin films was determined. The resistivity (\(\rho\)), conductivity (\(\sigma\)), mobility (\(\mu\)), carrier concentration and conduction type of the films were determined using Hall Effect measurements. The interesting optical properties of CuInGaS2 make them an attractive material for photovoltaic devices.